The present invention relates generally to pressure responsive valve assemblies. More particularly, the present invention relates to pressure responsive valve assemblies which include suction reed valves. The valve assemblies are adapted for use in reciprocating piston type compressors, such as refrigeration type compressors.
Reciprocating piston type compressors typically employ suction and discharge pressure activated valving mounted at the end of the cylinder housing. When designing these valve assemblies, it is of critical importance to the operation of the overall system to provide a sufficiently large port area in order to permit the flow of a maximum amount of gas within a given time period and with an acceptably small pressure drop. This is particularly true for refrigeration compressors employed in air conditioning systems because of the high mass flow rates generally required in such systems.
Associated with and conflicting with the desirability to maximize port area for a given cylinder size, is the need to reduce the weight of the moving valve member. The reduction of the weight of the moving valve member will lead to a reduction of the inertial effect of the valve and the reduction of the noise level associated with the opening and closing of the valve.
Another import design objective is to minimize the re-expansion or clearance volume of the cylinder. The valving system and the cylinder end top end wall should have a shape which is complimentary with the shape of the piston to reduce the volume of the compression chamber to a minimum when the piston is at top dead center of its stroke without restricting gas flow. While it may be possible to accomplish this objective by designing a complex piston head shape, manufacturing of this complex shape becomes excessively expensive, the assembly becomes more difficult and throttling losses generally occur as the piston approaches top dead center. This leaves the design for the valving system as the only means for designing a high-flow valving system which minimizes the re-expansion volume.
A typical suction reed includes a circular body which is used to cover a circular suction port in a valve plate. A pair of tabs extend radially outwardly from the circular section to provide means for attaching the suction reed to the valve plate. As the piston drops in the cylinder bore, the volume of the cylinder increases thus creating a vacuum in the bore. This vacuum pulls down the suction reed causing the suction reed to bend or deflect to open the suction port. While the suction reed is in this bent or deflected position, gas flows into the cylinder. Typically one of the tabs is riveted or otherwise secured to the valve plate to define a fixed side while the other tab is free to move when the compressor operates to define a free end side.
The shape or configuration of the reed affects how much the reed will deflect. The reed can be designed to provide the maximum flexibility for the reed, which will then create the best performance because it will open more to allow the maximum gas flow. The problem with this maximum flexibility design is that it creates the worst stress because generally, the more the reed moves, the more stress the reed experiences. Conversely, the reed can be designed to provide the best stress resistance but this will cause a diminishment in the performance of the compressor.
The present invention provides the art with a reed design that has been optimized to provide the best flow characteristics while still possessing good resistance to both bending and impact stresses. The size of the reed outside diameter (OD), the inside diameter (ID), thickness, neck shape, neck down radius and clamp line location have been designed to create a unique reed that provides low stress to the reed while providing enough flexibility for the reed to allow for good performance of the compressor.
In addition to the flexibility and bending stress design considerations for the reed of the present invention, the unique reed design of the present invention is also designed to account for impact stress. If the reed OD/ID ratio is made too large (i.e. the ring portion of the reed is too wide), the reed will be too stiff and it will not deflect enough to provide adequate gas flow. If the reed OD/ID ratio is made too small (i.e. the ring portion of the reed is too narrow), the impact stress on the reed will be too high and the reed will fracture. The unique reed of the present invention is designed with an optimal OD/ID ratio to create a reed that has superior performance.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.